function deltm=fun1(t1)
tf=t1+2.4;
V0=pi*5^2*500;rou0=0.85;
m0=rou0*V0;
[ti,mhat]=ode45(@(t,m)myqn1(t,m,t1),[0:0.01:tf],m0);
deltm=mhat(end)-m0;